Operation and maintenance manual

Section 250-0070
Braking System - Treadle Valve
SM 2165 Rev 1 11-03
4
leakage is not coming from there.
2. Failure of the pedal to return to full upright position.
3. Treadle valve holds pressure when in the neutral
position.
4. Varying output pressure with the pedal fully
depressed.
5. Output pressure tolerance for upper circuit should be
within +/- 6.9 bar (+/- 100 lbf/in²).
6. Output pressure tolerance for lower circuit should be
within +/- 6.9 bar (+/- 100 lbf/in²).
REMOVAL
WARNINGS
To prevent personal injury and property
damage, be sure wheel blocks are properly
secured and of adequate capacity to do the job
safely.
Hydraulic oil pressure will remain
within the system after engine shut down.
Operate the treadle pedal continuously until
the pressure has dissipated before carrying
out any work on the braking system or serious
injury could result.
1. Position the vehicle in a level work place, raise the
body and secure in place with the body prop. Apply
the parking brake, switch off the engine and turn
steering wheel in both directions several times to
relieve any pressure in the steering circuit.
2. Operate the treadle valve continuously to relieve
pressure in the braking system. Block all road wheels
and place battery master switch in the 'Off' position.
3. Pull on handle to release hood catch and lift up
hood.
4. Remove blanking cap from remote drain line at the
bottom of the hydraulic tank. Install a length of hose on
remote drain fitting, open drain cock and drain
hydraulic oil into a suitable container. Close drain
cock, remove hose and reinstall blanking cap.
5. Move cab floor mat back and remove bolts and
lockwashers securing service access plate to cab
floor.
6. Clean treadle valve assembly and surrounding area
with a suitable solvent. Ensure all hydraulic lines
connected to the treadle valve are identified for ease of
installation and, with suitable containers available to
catch leakage, disconnect hydraulic lines. Fit blanking
caps to all open lines and treadle valve ports.
7. Tag and disconnect electrical connections from the
proximity switch and stop light pressure switch.
8. Tag and disconnect electrical connections from the
kick-down switch and accelerator pedal assembly.
9. Remove service access panel and attached valve
assemblies to a clean area for 'Disassembly'.
10. Release and remove mounting hardware securing
the treadle valve to the service access plate. Remove
treadle valve assembly to a clean area for further
'Disassembly'.
DISASSEMBLY
Numbers in parentheses refer to Fig. 1.
1. Remove blanking caps from treadle valve ports and
drain all oil from valve body ports by rotating the valve
over a suitable container.
2. Secure the valve assembly upright in a table vice.
3. Remove pedal (1) from actuator cam by loosening
two capscrews at the pedal heel. Note that capscrews
need not be removed.
4. Loosen but do not remove nuts from 'U' bolts
securing actuator pivot pin (2).
5. Loosen nut securing proximity switch (28) to
actuator base and remove.
6. Remove pivot pin (2) from actuator base (3) with a
punch and hammer. Remove actuator cam assembly
and inspect for any abnormal wear or cracks. Set
aside for assembly.
7. Remove boot (5) from pilot valve body (8).
8. Remove capscrews securing actuator base (3) to
pilot valve body (8). Remove actuator base (3) from
pilot valve body (8).
9. Remove adjusting screw (4) from pilot valve body (8).
10. Remove valve assembly from the vice.